boards: st: stm32h573i_dk: Add board variant for app in external flash

Restore old internal flash layout as default and make app in external
flash a new board variant

Switch mcuboot to use swap mode and remove the no longer required
scratch partitions from the internal and external flash layout.

Introduce a 'soc-nv-flash' node in the stm32h573i_dk board DTS file
to define the external flash memory parameters used for MCUBoot
integration. This way BOOT_MAX_IMG_SECTORS_AUTO can be used to
automatically calculate the maximum number of image sectors based
on the actual external flash configuration.

Signed-off-by: Tim Pambor <[email protected]>

Author: tpambor

boards/st/stm32h573i_dk/Kconfig.sysbuild

@@ -0,0 +1,18 @@
+# SPDX-FileCopyrightText: Copyright The Zephyr Project Contributors
+# SPDX-License-Identifier: Apache-2.0
+
+choice BOOTLOADER
+	default BOOTLOADER_MCUBOOT
+endchoice
+
+choice BOOT_SIGNATURE_TYPE
+	default BOOT_SIGNATURE_TYPE_NONE
+endchoice
+
+if BOARD_STM32H573I_DK_STM32H573XX_EXT_FLASH_APP
+
+choice MCUBOOT_MODE
+	default MCUBOOT_MODE_SWAP_USING_OFFSET
+endchoice
+
+endif # BOARD_STM32H573I_DK_STM32H573XX_EXT_FLASH_APP

boards/st/stm32h573i_dk/board.yml

@@ -4,3 +4,5 @@ board:
   vendor: st
   socs:
     - name: stm32h573xx
+      variants:
+        - name: ext_flash_app